This invention relates to a fiber optic apparatus for producing an approximately uniform scattered light output, and particularly to improvements on two types of fiberoptic diffusers which can be used in a biological environment, and methods of manufacturing the same.
The method known as "photodynamic therapy" (PDT) has been widely used in recent years in treatment for cancers or tumors, and other diseases in humans and even in animals. Reference is made to U.S. Pat. No. 4,889,129 for a discussion of particulars of one such PDT method and apparatus for practicing the method. There are three types of optical devices which are mainly used in PDT for light distribution at the treating region. The fiber optic microlens is one type of device which can transfer a divergent light beam to an area of accessible tissue surfaces. The fiber optic cylindrical diffuser or "line source" is another type which has a cylindrical scattering pattern of light output with respect to the central axis of the optical fiber, and can be used in a cylindrical geometry for application to areas such as a bronchus or esophagus. The fiber optic spherical diffuser or "light bulb" is the third type of device which produces a spherical scattering light field. The spherical diffuser is usually applied in treatment to approximately spherical cavities, e.g. the bladder or a surgically created cavity resulting from the resection of the bulk of a tumor.
A typical example of a fiber optic cylindrical diffuser and a method of making the same is disclosed in U.S. Pat. No. 4,660,925 issued on Apr. 28, 1987 to James S. McCaughen, Jr. The cylindrical diffuser disclosed by the MaCaughan patent includes an optical fiber with an exposed core portion at one end, a scattering medium coated on the exposed core portion and on the sheathing of the fiber adjacent thereto, and an end-open tube adhered on the scattering medium. The process of manufacturing the diffuser mainly includes the steps of stripping the cladding and sheathing of the fiber at one end of the fiber to provide a length of exposed fiber core, polishing the exposed core, coating the exposed core and the adjacent sheathing with a scattering medium, tightly inserting the scattering medium into the tube, filling interstices between the earlier coated scattering medium and the tube with the scattering medium, and excluding the entrapped air.
A typical fiber optic spherical diffuser and a method of making the same are shown by the U.S. Pat. No. 4,693,556 issued on Sept. 15, 1987 to James S. McCaughan, Jr. The method mainly includes the steps of removing the cladding and sheathing of an optical fiber at one end to provide an exposed core portion, polishing the exposed core portion, and coating the exposed core portion and the adjacent sheathing of the fiber layer by layer with a scattering medium until a scattering sphere is formed.
In photodynamic therapy, the basic requirements for the fiber optic diffusers are that the light distribution must be as uniform as possible within a volume of tissue containing a tumor, and the mechanical properties must be reliable. If the fiber optical diffuser assembly breaks on insertion or during treatment, the light distribution will be inadequate at best. Furthermore, there is a possibility that a piece of the broken fiber will be left behind and if elevated oxygen concentration is present the danger of fire exists because of the higher power density present at the broken end of the fiber. In addition, rigidity of the fiber optic diffuser is also an important requirement in PDT. This is because the path of the fiber assembly in a channel of a flexible endoscope and in a tumor should be controlled by the direction of insertion rather than the irregular mechanical properties of the tissue or tumor. It is also desirable that the fiber optic diffusers have a low power loss and maximum power handling ability.
These requirements are not well satisfied by the conventional devices due to the shortcomings in their structures or the methods of making them.
The present invention is an improvement on the prior fiberoptic diffusers including the prior fiberoptic cylindrical diffusers and fiberoptic spherical diffusers, and on the methods of manufacturing the same.